What are the benefits of having the dental transillumination test?

Fracture ID. Dentists often use transillumination as a way to look for fractures inside teeth. It is a bright light that shines on the tooth and can make internal problems more evident. It is painless, and helps identify or confirm hidden problems.
Cracked teeth. Often it is extremely difficult to see if a tooth has cracked visually or on a dental radiograph (x-ray). By shinning light on a tooth, the dentist can detect breaks in the enamel matrix that are sharply contrasted due to the light not uniformly penetrating the area . Cracks can easily be detected. Cracked teeth can lead to dental pain and tooth loss if left untreated.
Highlights defects. Dental transillumination test highlights the defects that are not easily seen inside the tooth.